Fluoropolymer compositions containing fluoropolymers which comprise ionisable groups are known from the prior art.
For example, U.S. Pat. No. 5,498,457 (HITACHI) relates to a magnetic recording medium having a lubricant layer comprising ionically interbonded fluoropolyethers with acidic and basic terminal groups; preferably, each fluoropolyether has at least two acidic terminal groups or basic terminal groups in one molecule. According to a specific embodiment, the fluoropolyether containing acidic terminal groups complies with formula:HO2C(CF2O)n(CF2CF2O)mCF2CO2H,wherein m and n are integers, while the perfluoropolyether containing basic terminal groups complies with formula:H2NHCH2CHN(O)C(CF2O)n(CF2CF2O)mCF2C(O)NHCH2CH2NH2,where m and n are integers. U.S. Pat. No. 5,498,457 does not disclose or suggests polymer mixtures based on fluoropolyethers containing recurring fluoropolyether blocks and recurring cationic or anionic blocks wherein at least one of the cationic or anionic blocks is between two fluoropolyether blocks.
WO 2010/000715 (SOLVAY SOLEXIS SPA) and WO 2008/138927 (SOLVAY SOLEXIS SPA) disclose compositions comprising at least a (per)fluoropolyether derivative which contains at least one fluorinated block and at least one urethane block of formula:—OC(O)—NH-E-NH—C(O)O—wherein E is a divalent hydrocarbon group, optionally comprising one or more aromatic rings. The fluorinated block may contain at least one functional block comprising at least one ionisable group, like a sulfonic acid group, a carboxy group or an amino group. These documents do not disclose or suggest compositions comprising (per)fluoropolyether derivatives with opposite charges, i.e. at least one (per)fluoropolyether derivative comprising fluorinated blocks containing at least one ionisable anionic group and at least one (per)fluoropolyether derivative comprising fluorinated blocks containing at least one ionisable cationic group in a defined ratio of ionic equivalents. Furthermore, these documents do not teach or suggest using the compositions for preparing materials endowed with elastic and/or self-healing properties.
WO 2007/102993 (3M INNOVATIVE PROPERTIES CO) relates to surface active block copolymers, their use in the manufacture of a foam composition and articles comprising the polymerised foam composition. The fluorinated block polymers comprise a (per)fluorinated block and may also contain functional blocks typically having one or more polar groups, such as carboxy, sulphonic or amino groups. Also this document does not specifically disclose or suggest compositions comprising block copolymers containing functional blocks having opposite charges in a defined ratio of ionic equivalents.
WO 2010/028226 (ARROWSTAR LLC) discloses compositions for imparting water and oil repellency to fibers, the compositions comprising a fluorinated polyurethane having a plurality of ionisable groups. This document discloses in particular a mixture of a cationic fluorinated polyurethane, namely Fluorolink® 5032 polyurethane, and an anionic fluorinated polyurethane, namely Fluorolink® P56 polyurethane; the compositions further comprise an acrylic polymer and are in the liquid form. Example 2, in particular, discloses an aqueous composition containing 8.8% by weight Fluorolink® 5032 polyurethane and 30.0% by weight Fluorolink® P56 polyurethane. From the Applicant's calculations, it appears that the two polymers are not present in a stoichiometric equivalent ratio of ionic groups with opposite charges. Indeed, the equivalent weight of Fluorolink® 5032 polyurethane is 0.25 eq/kg and the equivalent weight of Fluorolink® P56 polyurethane is 0.49 eq/kg; accordingly, in the compositions of example 2, the equivalent ratio between Fluorolink® 5032 polyurethane and Fluorolink® P56 polyurethane is calculated to be 0.2, while the equivalent ratio between Fluorolink® P56 polyurethane and Fluorolink® 5032 polyurethane is calculated to be 6.7.
This document does not teach or suggest replacing water in the preparation of the above compositions and it does not teach or suggest submitting the compositions to cross-linking in order to obtain self-healable and resistant compositions.
WO 2011/131547 (SOLVAY SOLEXIS SPA) relates to an aqueous composition comprising at least one fluorinated polymer (F), at least one functional hydrogenated polymer (H) and at least one cross-linking agent and to the use of the composition as coating, varnish or paint, wherein the ratio of the polymer (F) to polymer (H) is higher than 0.75. Non aqueous compositions are neither mentioned nor suggested.
U.S. Pat. No. 5,798,409, corresponding to EP 0784641 B (MINNESOTA MINING AND MANUFACTURING COMPANY) discloses both aqueous and non-aqueous two-part polyurethane compositions and optionally self-healable and scratch-resistant coatings prepared therefrom.
In particular, the non-aqueous composition comprises a part A and part B, wherein part A may comprise a urethane prepolymer which may contain carboxylic acid functional groups and which has a defined average hydroxyl functionality and a defined hydroxyl equivalent-weight, while Part B contains a cross-linker from the group consisting of polyisocyanates, blocked polyisocyanates, and mixtures thereof and an organic solvent. The NCO:OH ratio of Part B to Part A ranges from about 0.95:1 to about 1.07:1. These compositions are said to provide a PUR having excellent scratch resistance and self-healability (reference is made in particular to par. [0020]). However, this document neither discloses nor suggests to prepare compositions containing two fluorinated ionizable PUR polymers having opposite charges and it does not teach or suggest to submit such compositions to cross-linking.
WO 2013/017470 (SOLVAY SPECIALTY POLYMERS IT) discloses self-healing polymer compositions comprising:
a) at least one fluorinated ionisable polymer (A), which comprises recurring fluorinated blocks and recurring functional blocks, each of said recurring functional blocks comprising at least one ionisable anionic group, and in which polymer (A) at least one of the said recurring functional blocks is comprised between two fluorinated blocks;
b) at least one fluorinated ionisable polymer (B), which comprises recurring fluorinated blocks and recurring functional blocks, each of said recurring functional blocks comprising at least one ionisable cationic group, and in which polymer (B) at least one of the said recurring functional blocks is comprised between two fluorinated blocks;
wherein the ratio between the ionic equivalents of polymer (A) and the ionic equivalents of polymer (B) ranges from 1.1 to 0.9.
Polymers A and B can be ester, polyester, polyurethane or acrylate polymers.
The above compositions can be used for manufacturing articles like sealing agents, gaskets and membranes or for manufacturing coatings for substrates like leather, paper or cotton. Certain compositions wherein the (per)fluoropolyether chains in polymers (A) and (B) have similar molecular weight are rubber-like materials endowed with self-healing properties at room temperature, i.e. they possess an intrinsic ability to repair mechanical damages without melting and cooling.
Two alternative methods are disclosed in this application for the manufacture of the above compositions. The first one is a so-called dispersion precipitation method which comprises the following steps:
a) preparing a dispersion of at least one polymer (A) and a dispersion of at least one polymer (B) in water or in a mixture of water and an organic solvent;
b) mixing together the dispersion of polymer (A) and the dispersion of polymer (B) until complete precipitation of a solid polymer composition;
c) filtering off the precipitated solid polymer composition;
d) washing and drying the precipitated polymer composition.
The second one comprises hot mixing at least one polymer (A) and at least one polymer (B).
In fact, in the dispersion precipitation method, polymers (A) and (B) are used in the salified form; however, compositions obtained according to this method are contaminated by salts (usually triethylammonium chloride); this salt contamination has a negative impact on the swelling properties of the compositions in water. Furthermore, this method does not allow preparing stable dispersions which can be stored for a certain time period and used subsequently.